A wiper blade, which wipes raindrops and the like adhered to a front glass surface of a vehicle, is disclosed in, for example, Japanese Unexamined Patent Publication No. S57-55244.
The wiper blade disclosed in this document uses a tournament type lever assembly, which includes one primary lever, two secondary levers and two yokes. The primary lever is connected to a wiper arm. The secondary levers are rotatably connected to ends, respectively, of the primary lever. The yokes are rotatably connected to corresponding ends of the secondary levers, respectively. Six holding claws are provided to six points of the assembly, i.e., ends of the yokes and the remaining ends of the secondary levers (ends other than the ends connected to the yokes) to hold the blade rubber. Backings, each of which has a length that is generally the same as that of the blade rubber, are installed to the blade rubber, and the blade rubber is held by the holding claws at the points where the backings are installed.
Each backing is made from a metal plate material and is formed into a straight shape (a linear shape) or a curved shape that has a predetermined curvature in the longitudinal direction thereof, and the backing has a resiliency in a plate thickness direction thereof. The urging force of the wiper arm is spread in the longitudinal direction of the blade rubber through the lever assembly and the backings, so that contact pressures of the blade rubber against the glass surface are unified in the longitudinal direction of the blade rubber.
A curvature of the front glass of the vehicle changes from one wiping angular position to a next wiping angular position of the wiper blade. The wiper blade, which wipes such a glass surface, is required to always follow the complicatedly curved glass surface and to achieve a good wiping performance.
However, in the case of the wiper blade recited in the above document, the load applied to each holding claw is set only by the space between the holding claws to adjust the contact pressure against the glass surface in the longitudinal direction of the blade rubber.
The adjustment of the contact pressure largely depends on the experience and sense of a skilled technician, and a result of the adjustment is checked through, for example, experiments. Thus, when the wiping performance over the entire wiping area of the glass surface, which continuously changes its curvature depending on the wiping angular position, needs to be improved, a large amount of time is required. Furthermore, such adjustment and setting merely achieve a satisfactory wiping performance, which is determined to be satisfactory in view of a product test standard, and do not necessarily achieves the best wiping performance.
The present invention is made to addresses the above disadvantages. Thus, it is an objective of the present invention to provide a wiper blade partial pressure setting method and a wiper blade, which can easily and reliably improve a wiping performance over an entire wiping area of a wiping surface.